▎ 摘　　要

Hopping transport associated with the granular nature of nanocrystal arrays has led to the thought that nanocrystal-based devices might be incompatible with fast operation. Here, we explore the design of HgTe nanocrystal-based sensors operating in the short-wave infrared and with a very fast time response down to a few nanoseconds. To reach this goal, the design relies on a planar geometry to reduce the device capacitance. A strong in-built electric field is tailored via electrostatic control from two bottom split-gate electrodes, which promote the charge extraction. Through the use of graphene electrodes patterned over the two gate electrodes, we optimize the control on the electrostatic design of the p-n junction inside the nanocrystal array. Taking advantage of a high-k dielectric spacer, we demonstrate that the device can be operated under a low gate bias (<6 V). The split-gate photodetector are versatile as they can be used in either the phototransistor or diode mode, with the two gates voltages that are set to design isotype or diode-type heterojunctions. We finally highlight that the time response enabled by the planar diode configuration can be made much faster than the one associated with the conventional vertical geometry.